Effect of isothermal annealing and electromigration pre-treatments on the reliability of solder interconnections under vibration loading T. Laurila • J. Karppinen • J. Li • V. Vuorinen • M. Paulasto-Kro ¨ckel Received: 26 April 2012 / Accepted: 31 May 2012 Ó Springer Science+Business Media, LLC 2012 Abstract Effects of two pre-treatment methods, isother- mal annealing and DC-current stressing, on the reliability of solder interconnections under vibration loading has been studied in this paper. The results obtained show that: (1) isothermal annealing and DC-current stressing both com- promise the reliability of interconnections during testing in comparison to the samples without pre-treatment and (2) the crack propagation path through the interconnection changes as compared to the samples without pre-treatments. The experimental results are rationalized with the help of detailed microstructural investigations coupled with the finite ele- ment method analysis. The DC-current stressing and iso- thermal annealing pre-treatments both soften the solder interconnections by inducing microstructural changes, which is reflected in the slightly reduced reliability under vibrational loading. 1 Introduction When considering the entire lifespan of electronic products, multiple loading conditions take place both concurrently and consecutively during the service life. As an example, auto- motive electronics typically endure thermal loads from the operational environment (ambient outdoor temperature, heat from the combustion engine) and mechanical vibration loads originating from the automotive powertrain and suspension. Simultaneously, the electrical conductors and interconnections are stressed with high DC currents during operation. In order to successfully assess the reliability of electronic devices encountering such complex loading conditions, the damage mechanisms and interactions of all the different loads should be accounted for. However, to this date, the reliability implications of mul- tiple loads have been verified using standardized tests with individual loading conditions. This conventional approach results in an incomplete representation of the true use case, as the damages caused by different loads are not allowed to accumulate and interact between the tests. Even if the reli- ability effects of a single loading condition are not considered substantial by itself, the consequences on lifetime can be drastic when combined with other loading conditions. It is generally recognized that the overall reliability of contemporary electronics is to a large extent determined by the reliability of solder interconnections. Consequently, for example in microelectronic equipment with long service- life, the most common failure mechanism is solder joint fatigue due to thermal and mechanical loadings. To address this issue, several studies have been published lately on the reliability effects of combined thermal, thermomechanical, and mechanical vibration loads on solder interconnections. Eckert et al. [1, 2], Qi et al. [3, 4] and Basaran et al. [5] have studied the effect of combined mechanical vibration and thermal loading on the lifetime of ball grid array type interconnections. Manock et al. [6] have investigated the effects of consecutive isothermal annealing and thermal cycling on the reliability of solder joints in a plastic ball grid array package. Mattila and Kivilahti [7] have studied the effects of consecutive thermal cycling, annealing and drop testing on chip scale package flip-chip interconnec- tions. Finally, Su et al. [8] have studied the combined effects of electromigration loading, mechanical strain and elevated temperature on lead-free solder material. T. Laurila (&) Á J. Karppinen Á J. Li Á V. Vuorinen Á M. Paulasto-Kro ¨ckel Department of Electronics, School of Electrical Engineering, Aalto University, PO Box 13340, 00076 Aalto, Espoo, Finland e-mail: tomi.laurila@tkk.fi; tomi.laurila@aalto.fi 123 J Mater Sci: Mater Electron DOI 10.1007/s10854-012-0783-9